This grant proposal is a request for the renewal of funding for the Center for Membrane Toxicity Studies, an NIEHS Marine and Freshwater Biomedical Sciences Center (MFBS), located at the Mt. Desert Island Biological Laboratory (MDIBL) in Salisbury Cove, Maine. The goal of this Center since its inception in 1985 has been to involve a group of internationally recognized scientists, who are experts in mechanisms of epithelial transport, to study the biological effects of environmental pollutants on cell and membrane transport functions. The focus of these efforts has been to elucidate the mechanisms of toxicity and pathways of excretion of environmental toxicants at the cellular and molecular level using novel aquatic models developed at this laboratory. This Center grant facilitates this effort by providing: a) administrative and research facility support, b) pilot-feasibility grants to attract new investigators to work on Center goals, and c) community outreach and educational programs that include student education programs (minority and local high school students), and shared activities with environmental groups in local high schools. In addition to the Administrative Core, the Center is composed of 5 Facility Cores: an Animal Core, Instrumentation Core, Cell Isolation, Culture and Organ Perfusion Core, an Imaging Core, and a newly formed Bioinformatics Core. The Research Base of the Center includes a core group of 21 investigators (Bain, Baldwin, Ballatori, Barnes, Boyer, Callard, Dranoff, Forbush, Forrest, Fricker, Henson, Kinne, Kullman, Mattingly, Miller, Renfro, Riordan, Sate, Stanton, Villalobos and Xiao) who focus on two common research themes: 1) signal transduction and ion transport, and 2) xenobiotic transport and excretion. Investigators in the Pilot Feasibility Program also contribute to these research themes. While the research activities of this Center were traditionally seasonal, the Center's research base is now increasingly a year-round scientific activity both at the MDIBL and at the investigators' home institutions.